Composite Adsorbent Research Articles

Preparation of a novel CSM@ZIF-67 composite microsphere to facilitate Congo red adsorption from dyeing wastewater

ABSTRACT Chitosan (CS) is commonly used as an adsorbent for wastewater treatment because of its low cost, strong adsorption properties, and high availability of raw materials required for its production. However, CS exhibits limited adaptability to pH, poor mechanical properties, and high swelling in aqueous media; these limitations restrict its widespread use. To address these issues, herein, zeolitic imidazolate framework-67 (ZIF-67) is loaded onto crosslinked CS microspheres (CSM) to prepare CSM@ZIF-67, a composite adsorbent. Next, the CSM@ZIF-67 is applied to the treatment of Congo red (CR) dye, which is typically present in printing and dyeing wastewater. The results demonstrate that the in situ synthesis of metal-organic frameworks (MOFs) on CSM improve the dispersion of MOFs and preserve the morphology of the MOFs. The adsorption equilibrium of CSM@ZIF-67 is reached within 150 min, and its adsorption capacity is as high as 538.4 mg/g at a pH of 9 and temperature of 25 °C. The CR adsorption process is consistent with the pseudo-second-order kinetic and Langmuir isotherm models, thus revealing that chemisorption is the primary rate-limiting step, and the pollutants are adsorbed on the adsorbent surface in a monolayer. Experiments on material cycling and regeneration performance reveal that the removal efficiency of CSM@ZIF-67 remains above 90%, even after five rounds of adsorption. CSM@ZIF-67 has abundant functional groups and adsorption sites and can efficiently remove CR through mutual interactions between the metal coordination effect, π–π conjugation, hydrogen bonding, and electrostatic interactions.

Preparation of MIL100/MIL101-alginate composite beads for selective phosphate removal from aqueous solution

Numerous studies have reported various approaches for synthesizing phosphate-capturing adsorbents to mitigate eutrophication. Despite the efforts, concerns about production cost, the complexity of synthesis steps, environmental friendliness, and applicability in industrial settings continue to be a problem. Herein, phosphate-selective composite adsorbents were prepared by incorporating alginate (Alg) with MIL100 and MIL101 to produce the MIL100/Alg and MIL101/Alg beads, where Fe3+ served as the crosslinker. The unsaturated coordination bond of MIL100 and MIL101 serves as a Lewis acid that can attract phosphate. The adsorption equilibrium isotherm, uptake kinetics, and effects of operating parameters were studied. The phosphate adsorption capacity of MIL100/Alg (103.3 mg P/g) and MIL101/Alg (109.5 mg P/g) outperformed their constituting components at pH 6 and 30 °C. Detailed evaluation of the adsorbent porosity using N2 sorption reveals the formation of mesoporous structures on the Alg network upon incorporation of MIL100 and MIL101. The composite adsorbents have excellent selectivity toward anionic phosphate and can be easily regenerated. Phosphate adsorption by MIL100/Alg and MIL101/Alg was driven by electrostatic attraction and ligand exchange. Preliminary economic analysis on the synthesis of the adsorbents indicates that the composites, MIL100/Alg and MIL101/Alg, are economically viable adsorbents.

Preparation of metal organic frameworks modified chitosan composite with high capacity for Hg(II) adsorption

In this study, a novel modified chitosan composite adsorbent (UNCS) was prepared by crosslinking between chitosan and metal organic frameworks (MOFs) material UiO-66-NH2 using epichlorohydrin as crosslinker. The influence of the prepared conditions was investigated. The structure and morphology of the composite were characterized by FT-IR, XRD, SEM, TGA, BET and zeta potential analysis. Effects of different variables for adsorption of Hg(II) on this adsorbent were explored. The kinetic studies indicated that the adsorption process followed the pseudo-second-order kinetic model and the adsorption equilibrium could be reached within 2 h. The adsorption was mainly controlled by chemical process. Adsorption isothermal studies illustrated that the adsorption fitted Langmuir isotherm model, implying the homogeneous adsorption on the surface of the adsorbent. The adsorbent exhibited high uptake and the maximum capacity from Langmuir model could reach 896.8 mg g−1 at pH 6. Thermodynamic studies showed the spontaneous nature and exothermic nature of the adsorption process. Additionally, the removal of Hg(II) on UNCS could achieve over 90 %. The adsorption-desorption cycled experiments indicated the appropriate reusability of the adsorbent. Hence, this adsorbent would be promising for the removal of Hg(II) from wastewater.

Immobilization of 137Cs as a crystalline pollucite surrounded by amorphous aluminosilicate

To date, radiocesium (137Cs) has been considered stable in the form of pollucite mineralized through high-temperature heat treatment. This study presented a possibility through experimental results that the entire medium exists as amorphous aluminosilicate at a relatively low temperature, but cesium is partially and preferentially converted from a composite adsorbent into pollucite. Cesium lowers the eutectic point within the system and initiates the nucleation of pollucite prior to other elements. We confirmed that the partial mineral phase of cesium showed the same chemical stability as when the entire medium was converted to pollucite. X-ray absorption spectroscopy provided direct evidence for this phenomenon; also, the stability results of radioactive cesium shown through a series of sintering experiments supported the conclusion. This method can be applied as a method to immobilize radioactive cesium under relatively mild temperature conditions of atmospheric pressure, while eliminating the problem of diffusion due to its volatilization.

A Study on the Improvement of the Photothermal Characteristics of the Adsorbent for Sorption-Based Atmospheric Water Harvesting Driven by Solar

Facing the global freshwater resource crisis, using solar energy to produce fresh water resources in an environmentally friendly way, sorption-based atmospheric water harvesting driven by solar technology has attracted increasingly more attention. In the current research, the adsorbent MOF-801 has the advantages of a high adsorption capacity and is suitable for fields with a wide range of humidity. However, the strong interaction between the adsorbent and water molecules is conducive to rapid moisture absorption, but at the same time, the adsorbent needs higher heat to achieve regeneration, which restricts the practical application of the adsorbent. Based on the principle that carbon materials can improve the photothermal conversion performance of adsorbent, this paper prepared three composite adsorbents with MOF-801 and three different carbon materials, characterized the structure and morphology of each adsorbent, and compared the effects of different carbon materials on the performance of MOF-801 adsorbent. Among them, the photothermal characteristics of MOF-801/CNT adsorbent proposed in this paper are most significantly improved. The experiment shows that compared with MOF-801/G, the adsorption capacity is increased by 30%, and the desorption speed is increased by 50%. It maximizes water withdrawals over a period of time in arid environments.

Endowing Covalent Organic Frameworks with Photoresponsive Active Sites for Controllable Propylene Adsorption.

Photoresponsive covalent organic frameworks (PCOFs) have emerged as attractive candidates for adsorption, but it is challenging to construct PCOF adsorbents due to structural order loss of covalent organic frameworks (COFs) after introducing photoresponsive motifs and/or tedious steps of postmodification. Here, a facile strategy is developed, by dispersing photoresponsive metal-organic polyhedra (PMOP) into COFs, to endow COFs with photoresponsive adsorption sites. As a proof-of-concept study, a COF with pore size of 4.5nm and PMOP with suitable molecular size (4.0 and 3.1nm for trans and cis configuration, respectively) are selected to meet the requirements of proper accommodation space, good guest dispersion, and free isomerization. The structure of COF is well preserved after introducing PMOPs. Interestingly, the obtained photoresponsive host-guest composite (PHGC) adsorbents exhibit photomodulated adsorption capacity on propylene (C3 H6 ) and the change in adsorption capacity can reach up to 43.3% and is stable during multiple cycles. Density functional theory calculations reveal that visible-light irradiation drives the azobenzene motifs in PHGCs to the trans configuration and the adsorption sites are fully open and interact with C3 H6 . UV-light irradiation makes the azobenzene motifs transform to the cis configuration, leading to the shield of the adsorption sites and the consequent release of C3 H6 .

The Study on Kaolin/corn Stalk Composite Adsorbent Materials Prepared by H3PO4 Activation Method

Using single factor method and orthogonal experiment,the study takes Kaolin and corn straw as raw materials and H3PO4 as activator and dips them in different activator concentration,different kaolin and corn straw mass ratio as well as different impregnation ratio under different conditions, and then carbonize them in low temperature by electric furnace, muff calcining to prepare kaolin/corn straw composite adsorption material.The adsorption capacity for methylene blue solution was characterized by T6 visible spectrophotometer,and automatic specific surface area and porosity analyzer was used to characterize the composite adsorption material under the optimal experimental conditions. The results show that the optimal experimental conditions are: Under the conditions of 25% Concentration of H3PO4 , 1:4 mass ratio of kaolin to corn stalk and 2.5:1 impregnation ratio, the adsorption value of methylene blue on the composite adsorbent is 1.116mg/g, the specific surface area is 7.56m2·g-1 and the single specific surface area is 6.82m2·g-1. The microporous volume was 1.24×10-8mL·g-1 and the microporous area was 0.57m2·g-1，the results show that the pore structure of the composite adsorbent is not uniform, and there are a lot of micropores and a certain amount of mesopores in the samples.

Adsorption Sulfate from Wastewater by Using New Material

Using physical activation, a new composite adsorbent was prepared by modifying low-cost local adsorbent. This low-cost local adsorbent was also prepared from activating sludge, bentonite, and limestone (SBL). In comparison to the low-cost LCL, the adsorption capacity of the new composite adsorbent was improved. This was measured in terms of its ability to remove sulfate from wastewater. The behavior of the sulfate adsorption processes by using (SBL) as an adsorbent was investigated in batch experiments by examining different values of solution pH, contact time, adsorbent dose, and initial SO4 concentration. The high removal efficiency was exhibited by (SBL) = 96%. These results reveal the great potential of the new composite adsorbent (SBL) if applied to the absorption of sulfate ions.

Enhanced NH3 Adsorption Capacity of CuCl2 by Changing the pore structure

Ammonia is an important carrier of hydrogen energy, with the characteristics of high hydrogen content density and no carbon dioxide emission. In recent years, many methods of ammonia synthesis using biomass have been widely studied to improve ammonia yield. Therefore, safe and efficient ammonia capture for ammonia synthesis from biomass is an important way to alleviate the energy crisis and solve the energy problem. In this paper, the NH3 adsorption properties of CuCl2 were measured, and the composite adsorbents were prepared by using silicon and multi-walled carbon nanotubes respectively to support CuCl2, and the NH3 adsorption properties of the composite adsorbents were studied. The study found that the NH3 adsorption capacity of the three adsorbents decreased with the increase in temperature, so metal chlorides were more suitable for the low-temperature adsorption of ammonia. Silicon and multi-walled carbon nanotubes have an enhanced effect on the NH3 adsorption of CuCl2. The reason is that the porous material itself has a physical adsorption effect on ammonia, and silicon can play the role of skeleton support in cupric chloride particles, which enhances the pore structure of the adsorbent, thereby alleviating sintering.

Performance of a Solar-Biomass Adsorption Chiller

A dynamic model is presented for a chiller working with a composite adsorbent (silica activated carbon/CaCl2)–water pair in a solar-biomass cooling installation. The main objective is determining a link between two possible evaporator configurations and the refrigerator’s performances. The two considered evaporators work at different pressure levels. The related time evolution profiles of temperature, pressure and water content are studied. Moreover, the effects of hot water inlet temperature and cooling water inlet temperature on the specific cooling capacity (SCP) and coefficient of performance (COP) are predicted by means of numerical simulations. The results show that an increase in the temperature of hot water and a decrease in the temperature of the cooling water allow an increase in COP and SCP. In particular, for a hot water inlet temperature of 85°C and a cooling water inlet temperature of 40°C, the COP and Qev are 0.67 and 4.3 kW, respectively.

Elimination of aspirin and paracetamol from aqueous media using Fe/N-CNT/β-cyclodextrin nanocomposite polymers: theoretical comparative survey via advanced physical models.

The main purpose of this research is to theoretically investigate the adsorption of two pharmaceutical molecules, i.e. aspirin and paracetamol, using two composite adsorbents, i.e. N-CNT/β-CD and Fe/N-CNT/β-CD nanocomposite polymers. A multilayer model developed by statistical physics is implemented to explain the experimental adsorption isotherms at the molecular scale, so as to overpass some limitations of the classical adsorption models. The modelling results indicate that the adsorption of these molecules is almost accomplished by the formation of 3 to 5 adsorbate layers, depending on the operating temperature. A general survey of the number of adsorbate molecules captured by the adsorption site (npm) suggested that the adsorption process of pharmaceutical pollutants is multimolecular and that each adsorption site can capture several molecules simultaneously. Furthermore, the npm values demonstrated the presence of aggregation phenomena of aspirin and paracetamol molecules during adsorption. The evolution of the adsorbed quantity at saturation confirmed that the presence of Fe in the adsorbent enhanced the removal performance of the investigated pharmaceutical molecules. In addition, the adsorption of the pharmaceutical molecules aspirin and paracetamol on the N-CNT/β-CD and Fe/N-CNT/β-CD nanocomposite polymer surface involved weak physical type interactions, since the interaction energies do not overcome the threshold of 25 000 J mol-1.

Coconut power: a sustainable approach for the removal of Cr6+ ions using a new coconut-based polyurethane foam/activated carbon composite in a fixed-bed column.

To attain efficient removal of hexavalent chromium (Cr6+) from aqueous solutions, a novel polyurethane foam-activated carbon (PUAC) adsorbent composite was developed. The composite material was synthesized by the binding of coconut shell-based activated carbon (AC) onto a coconut oil-based polyurethane matrix. To thoroughly characterize the physicochemical properties of the newly developed material, various analytical techniques including FTIR spectroscopy, SEM, XRD, BET, and TGA analyses were conducted. The removal efficiency of the PUAC composite in removing Cr6+ ions from aqueous solutions was evaluated through column experiments with the highest adsorption capacity of 28.41 mg g-1 while taking into account variables such as bed height, flow rate, initial Cr6+ ion concentration, and pH. Experimental data were fitted using Thomas, Yoon-Nelson, and Adams-Bohart models to predict the column profiles and the results demonstrate high breakthrough and exhaustion time dependence on these variables. Among the obtained R2 values of the models, a better fit was observed using the Thomas and Yoon-Nelson models, indicating their ability to effectively predict the adsorption of Cr6+ ions in a fixed bed column. Significantly, the exhausted adsorbent can be conveniently regenerated without any noteworthy loss of adsorption capability. Based on these findings, it can be concluded that this new PUAC composite material holds significant promise as a potent sorbent for wastewater treatment backed by its excellent performance, cost-effectiveness, biodegradability, and outstanding reusability.

Porous boron nitride nanofibers enhanced sodium acrylate and acrylamide copolymer hydrogels for effective adsorption of Pb2.

A new composite hydrogel adsorbent for adsorption of Pb2+ has been prepared by combining porous boron nitride nanofibers (BNNFs) and the acrylamide and sodium acrylate copolymer (P(AANa-co-AM)) via a chemical crosslinking method. Porous BNNFs with abundant hydroxyl functional groups can form hydrogen bond interactions with carboxyl and amino functional groups of the copolymer in the composite hydrogel and carry and dissipate forces for the composite hydrogels. So the mechanical performances of the copolymer hydrogels can be effectively improved, which is very valuable for the practical application of the composite hydrogel to remove Pb2+ from waste water. The thermal stability and swelling performance of the pure copolymer hydrogels were also greatly improved. This is not only because of the strong hydrogen bond interactions but also the good thermal stability and flexibility of BNNFs. The composite hydrogel adsorbent shows superior adsorption capacity for Pb2+ (490.2 mg g-1) to most of the reported hydrogel adsorbents. The chemisorption dominates the whole adsorption process according to the pseudo-second-order kinetic and the Langmuir models. The composite hydrogel adsorbent also shows good reusability. Therefore, we believe that the prepared composite hydrogels will play an important role in removing Pb2+ from wastewater.

Optimization of the Fabrication of Sustainable Ceramsite Adsorbent from Coal Fly Ash/Waterworks Sludge/Waste Glass for Decolorization of Malachite Green

As a traditional dye, malachite green (MG) poses a threat to our environment and health. To decolorize MG, a composite ceramsite adsorbent composed of coal fly ash (CFA), sewage treatment sludge (STS), and waste glass (WG) with a quality ratio of 3 : 3 : 4, respectively, was prepared. The optimal preparation parameters were determined as follows: preheating [Formula: see text], sintering [Formula: see text], and sintering [Formula: see text]. Under optimal conditions, scanning electron microscopy (SEM) images show that the X-Com-ceramsite sample exhibits rough features and a porous structure. The obtained X-Com-ceramsite has a good MG decolorization effect (92% decolorization rate with an initial MG concentration of 56.876 mg/L). The [Formula: see text] value of MG can reach up to 37.6 mg/g. The retention degree of MG in the X-Com-ceramsite with a relatively higher pH is stronger, and the adsorption process is spontaneous and endothermic. Synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS), and Fourier transform infrared spectroscopy (FT-IR) proved that the sensitivity of the C-O/C-O-O functional groups of the carbohydrates on the surface of the X-Com-ceramsite has a higher binding affinity toward MG as the initial concentration of MG changes.

Utilization of Wheat and Pigeon Pea Husk Adsorbents to Remove Copper and Nickel from Industrial Wastewater

The importance of the removal of heavy metals from industrial wastewater has received immense attention due to the increase of industrialization and heavy metals potential to harm human health. Different conventional methods are used for removing heavy metal contamination, but these methods have several disadvantages. Adsorption process is a simple, economical, and effective method to remove toxic heavy metals from industrial wastewater, but conventional adsorbents are neither readily available nearby nor economic therefore agro-based adsorbents are developed with chemical and thermal treatment. Developed adsorbents from the wheat husk and pigeon pea husk are used in filter units as filter media in combination with sand and aggregate. Activated wheat husk and pigeon pea husk adsorbents significantly removed Cu with 75.42% and 77% efficiency respectively and Ni with 72.50% and 74.17% respectively from industrial wastewater. This paper also studied the removal efficiency by varying pH and turbidity in synthetic solutions. The extent of removal of heavy metals by developed agro-based adsorbents is also correlated by proximate analysis, fixed carbon content 30 to 32%, bulk density 0.42 to 0.61 g/cc, iodine number 75.34 to 852.31, and chemical composition of adsorbents containing SiO2 . Characterization of prepared adsorbents also supported that developed adsorbents have great potential to carry the adsorption process to remove heavy metals from water and wastewater.

Synthesis of composite adsorbent based on Spent Mushroom Substrate (SMS) and Spent Bleaching Earth (SBE)

Synthesis of composite adsorbent based on Spent Mushroom Substrate (SMS) and Spent Bleaching Earth (SBE)

Preparation of citric acid/porous starch composite adsorbents and their adsorption studies

Citric acid (CA)-based polymeric adsorbent materials were fully characterized and analyzed for the adsorption treatment of methylene blue (MB). Also, the effects of various factors on their performance were thoroughly examined.

Removal of metals from water using MOF-based composite adsorbents

This review article focuses on metal–organic framework (MOF) composites and the impact of mixing MOFs with other materials, such as polymers, carbon-based materials, and magnetic particles, to increase their performance to remove metals from water.

In Situ Forming MnFe2O4/D201 Magnetic Composite Adsorbents for High Selectivity Adsorption and Deep Treatment of As(V) from Wastewater

A new magnetic adsorbent, namely, MnFe2O4/D201, with deep-treatment ability and high selectivity adsorption for As(V) was prepared. According to isotherm adsorption and kinetics, As(V) adsorption is primarily used for chemical bonding throughout the single-layer adsorbing process. The maximum As(V) adsorption capacity of MnFe2O4/D201 can reach 35.8 mg/g at pH 3. MnFe2O4/D201 also exhibits higher selectivity adsorption against Cl-, NO3 -, SO4 2-, and PO4 3-. According to the thermodynamic results, the adsorption process was spontaneous and endothermic. The adsorption capacity is maintained at 81% of the initial after ten adsorption-desorption cycles. As(V) concentrations ranging from 1 mg/L to 10 μg/L can be treated in fixed-bed column experiments. The effectual cure volume of As(V) reaches 1332 BV (26.64 L). The removal mechanism primarily comprises electrostatic attraction and complexation.

Valorization of agro-waste biomass as composite adsorbents for sustainable wastewater treatment

Agro-waste biomass in form of torrefied wheat straw (S) and oat hulls (Oh) were combined with kaolinite (K) and chitosan (Ch) to obtain pelletized adsorbent materials. The agro-waste pellets were compared to a common food-waste material in form of spent coffee grounds (SCG) as a reference biomass system. The composites were prepared with variable biomass content via physical blending and compared against their epichlorohydrin (ECH) crosslinked counterparts. IR and 13C NMR spectroscopy were employed for structural characterization of the composites, along with complementary thermogravimetric analysis. Composites with 80% Oh content were unstable and required ECH crosslinking, whereas their SCG and S counterparts were stable without crosslinking. A cationic methylene blue (MB) dye probe was employed to evaluate the adsorption properties of the pelletized materials. The Sips model was used to estimate the adsorption capacity (Qm), which was correlated with increasing biomass content: Qm = 22 ̶ 34 mg/g for the Oh composites, Qm = 21 ̶ 86 mg/g for the S composites, and Qm = 18 ̶ 98 mg/g for the SCG composites. Crosslinking notably reduced the adsorption capacity for both Oh and S composites, whereas greater MB uptake occurred for the SCG composites (Qm ∼ 135 mg/g). A cost-benefit analysis showed that S composites are competitive adsorbents for MB per dollar material cost versus SCG composites. Composites that contain torrefied biomass have lower chemical input costs that afford the design of sustainable adsorbent technology in a pelletized form.